REGIONAL COMPONENTS USED AS GROWING MEDIA IN ARGENTINA Osvaldo R. Valenzuela and Claudia S. Gallardo Facultad de Ciencias Agropecuarias de la Universidad Nacional de Entre Ríos C.C.nº (C.P. 00) Paraná, Entre Ríos, Argentina. Phone: + 0 9707. e-mail: osvaldov@fca.uner.edu.ar; cgallard@fca.uner.edu.ar Atelene N. Kämpf Bolsista de Pesquisa do CNPq nkampf@cpovo.net Keywords: plant substrates, organic and inorganic components, physical and chemical properties, South America. Abstract This study describes samples of 7 materials commonly used for seedling production in Argentina, with the objective to reduce the lack of literature on plant substrates in this country. The organic samples include two types of subtropical peat, pine bark at different grades of decomposition, vermicompost of diverse origins and carbonized rice hulls; the inorganic samples include: mineral soil, sand and others. The following characteristics were determined in three repetitions: total porosity (TP),dry bulk density (Ds), particle density (Dp); water retention capacity (WRC) at 0 hpa, airfilled porosity (AP), ph-value (ph) and salinity (EC). The peat from Delta de Entre Rios is fibrous with pieces of grass and ferns still present, has a high value of TP (between 8 and 9%v) and %v of WRC. The peat from Concordia is more mineralized, dark colored, with high WRC (6%v), low ph (from. to.) and EC value from 0.0 to ds/m ( o C). Pine bark presents TP > 8%v with WRC varying between 0 and 9%v and ph from. to.6. Vermicompost is a very heterogeneous material, intensively used by small growers. The variability among the results was very significant (p < 0.00). The samples showed values of TP varying from 7 to 9%v and WRC between 0 and 66%v. Despite already in use as a component for plant substrates in Brazil, carbonized rice hulls remain almost unknown in Argentina, where its potential use should be studied, due to the local rice crop production. The very low WRC (ca. 0%v) of this material can be limiting for some uses. Concluding, this study opens a new line of investigation on qualified plant substrates to replace the present use of mineral soils and sand materials. INTRODUCTION The present low relation of the Argentinean Peso to the US-Dollar led local producers of forest plants, vegetables and ornamental plants to look for alternative materials to substitute imported products based on Sphagnum peat in Argentina. In the praxis, the materials are selected to be used based on its price, availability during the whole year and the growers experience (Valenzuela and Gallardo 00). There is a lack of literature data about the properties of these alternative components in our country. The objective of this
study was to describe physical and chemical properties of some materials commonly used in the container plant production, not including their mixtures. MATERIALS AND METHODS We describe samples of 7 materials: two types of Argentinean subtropical peat (n=0) from Delta and Concordia of the Entre Rios State; pine bark with different grades of decomposition (n=0); vermicompost of different origins (n=); carbonized rice hulls (n=) and others (n=9) as sand, mineral soil, leaf mould and compost, where n is the number of analyzed samples in the laboratory. The following characteristics were determined in three repetitions: total porosity (TP) after the dry bulk density (Dd) and the particle density (Dp); water retention capacity (WRC) at 0 hpa and air-filled porosity(ap) according to the methods of de Boodt et al. (97). The ph-value (ph) and salinity (EC) were analyzed by saturation extract (Warncke 986) and the level of organic matter (OM) by calcination (0 ºC, h). RESULTS AND DISCUSSION Table shows the average values of ph (H O) and salinity - expressed as EC - of the analyzed materials, summarizing the large heterogeneity among these components. The two types of subtropical peat are very different, although both of them are sandy. The peat from Delta of the Entre Rios State is more fibrous with pieces of grass and ferns still present; it has a high TP (between 8 and 9%v) and %v of WRC (Fig. ), while the peat from Concordia is more mineralized, dark colored, with higher WRC (6%v). The ph values are low, varying from. to.; the salinity, expressed as electrical conductivity in the saturated extract, varies from 0.0 to ds m - ( o C), considered acceptable to be used as growing media in nurseries and for potted plants (Abad et al., 99). Pine bark is a very important component for mixtures already used by local producers of forest plants (Garcia et al. 00). The samples differ significantly (p< 0.00) in the analyzed characteristics, probably due to the maturity of the compost and to the particle size (Fig. ). In average, pine bark presented TP > 8%v with WRC varying between 0 and 9%v and ph from. to.6. Vermicompost is an intensively used component of mixtures by small growers, specially because its nutritional value. It is a very heterogeneous material and its quality depends on the source and the procedures to be obtained (Valenzuela et al. 998). These fact can explain the very significant variability among the results (p< 0.00). The samples showed values of TP from 7. to 9.%v and WRC values between 0 and 66.%v (Fig. ). Despite its high value as a component for plant substrates and the local rice crop production, carbonized rice hulls remain almost unknown in this region, where its potential use should be studied. Under the physical properties point of view, a very low WRC (ca. 0%v) of this material can be limiting for some uses (Fig. ). Other materials like mineral soil, sand and leaf mould (Fig. ) showed less appropriated characteristics for the use as substrates. Although its unsustainable exploration, these components remain still very used in the production systems in this region. The large heterogeneity among the studied materials and their properties indicates that they must be adapted in order to achieve the desired ranges for a good plant substrate.
Concluding, this study opens a new line of investigation on qualified plant substrates to replace the present use of mineral soils and sand materials. Literature Cited Abad, M., Martínez Herrero, M.D., Martínez García, P.F. and Martínez Corts, J. 99. Evaluación agronómica de los sustratos de cultivo. Actas de Horticultura :-. De Boodt, M., Verdonck, O. and Cappaert, L. 97. Method for measuring the water release curve of organic substrates. Acta Horticulturae 7: 0-06. García, M.A., Díaz, D., Alorda, M., Gallardo, C. and Valenzuela, O. 00. Características de los sustratos utilizados por los viveros forestales. IDIA XXI (in edition). Valenzuela. O.R. and Gallardo, C.S. 00. Los sustratos: un insumo clave en los sistemas de producción de plantines. IDIA XXI, Año III Nº, Horticultura y Floricultura: -9. Valenzuela, O.R., Lallana, V.H. and Guerrero, A. 998. Caracterización física y química de lombricompuestos originados a partir de residuos de conejeras, estiércol vacuno y residuos domiciliarios. Revista Científica Agropecuaria :-8. Warncke, D.D. 986. Analyzing greenhouse growth media by the saturation extraction method. HortScience (): -. Tables Table. Average values of ph and salinity (ds m - o C, SME) of materials used as component of growing media in Argentina. Materials ph (H O) EC (ds m - ) Subtropical peat Delta. -. 0. -. Subtropical peat Concordia. -. 0.0 -.0 Pine bark. -.6 0.09 -. Vermicompost. - 9 0.7 -.6 Carbonized rice hulls 6. - 8. 0.6 -.7 Rice hulls (in natura) 6.70 0.90 Mineral soil.0.00 Sand (fine) 7.60 0.60 Leaf mould. - 6. 0. -.
Figures Subtropical Peat (Delta) Subtropical Peat (Concordia) 0 0 0 60 80 00 0 0 0 60 80 00 A B Fig. : Solid:Pores relation in samples of subtropical peat (A. Delta of Entre Rios River; B. Concordia; Argentina) at water tension of 0 hpa. WCR = Water retention capacity; AP = air porosity; TS = total solids. 9 Pine Bark 7 0 0 0 60 80 00 Fig. : Solids:Pores relation in samples of pine bark in Argentina, at water tension of 0 hpa. WCR = Water retention capacity; AP = air porosity; TS = total solids.
EC (ds m - ) 0 8 6 9 6 0 7 0 0 0 0 sample number 0 0 0 0 0 0 60 70 80 90 00 A B Fig.. Vermicompost in Argentina: A. Electrical conductivity (EC, ds m - ); B. Solids:Pores relation at water tension of 0 hpa. WCR = Water retention capacity; AP = air porosity; TS = total solids. Values of samples. Carbonized Rice Hulls 0 0 0 60 80 00 Fig.. Carbonized rice hulls in Argentina: Solids:Pores relation at water tension of 0 hpa. WCR = Water retention capacity; AP = air porosity; TS = total solids.
Other Materials 9 8 7 6 Materials: fine sand mineral soil leaf mould leaf mould leaf mould compost compost rice hulls in natura perlite 0 0 0 60 80 00 Fig.. Other materials commonly used as components for plant substrate in Argentina. Solids:Pores relation at water tension of 0 hpa. WCR = Water retention capacity; AP = air porosity; TS = total solids.